260 P. SOUPART 
ways: with a single refrigerated photomultiplier (for #C only); with photomultipliers 
applied on both faces of cell and with photomultipliers placed at right angle, the same 
face of the cell facing both tubes with a prism interposed as a light-guide. The 
device fits, by means of a special adapter when necessary, in most commercial 
units currently used for the liquid scintillation counting of weak beta emitters. It 


to counting Za 
rarest 
i 
air pressure 





Fig. 13. Device for the counting of individual samples. 
may also be used for counting of individual samples by means of a device shown 
in Fig. 13. When the sample is counted, the stopper is put onto the next tube after 
wiping off the immersed part of the Teflon tubing with a piece of filter paper taking 
care not to introduce air bubbles. Due to the absence of mixing, rinsing with distilled 
water between successive samples is not necessary. The apparatus is calibrated 
with a standard solution which is run with each set of measurements. The reproduci- 
bility of the results as well as the linearity of response for solutions of increasing 
radioactivity are shown in Table XI. 
TABLE XI 
LINEARITY AND REPRODUCIBILITY OF SCINTILLATOR RESPONSE FOR MC 


Yield 
Counts/min (%, versus 
solution 3) 
Radioactivity 
(dilution factor) 

I) 1.000 28 895 100.6 
(stock solution) 
2) 0.332 9 478 99.4 
3) 0.201 5796-5789-5768 
5795-5774-575© 
Mean = 5775 100.0 
4) 0.1004 2851 98.9 
References p. 261/262 
